Microfluidic processes may use droplets as reaction vessels for performing chemical or biological reactions. In such processes, often referred to as droplet microfluidics, it may be desirable to increase the volume of the droplet by introducing additional fluid into the droplet. This ability allows significant dilution of the contents of a droplet, which may be desirable for controlling the concentration of substances within a droplet and enabling further partitioning or division of the contents of one droplet into multiple droplets for ease of handling or detection.
For example, to perform a simple enzymatic assay in one or more droplets, enzyme molecules and enzyme substrate may be introduced into the droplet by injection, followed by incubation and, typically, an optical detection step. In some cases, it may be desirable for the initial droplets to be divided into many droplets. In these instances, the initial droplet size may be too small, such that when the droplet is divided, the volume of the resulting droplets is insufficient for the remaining processes.
One solution to this is to increase the size of the droplet by adding picoliter size volumes of liquid to the droplets using, for example, picoinjection (e.g., Abate et al., “High-throughput injection with microfluidics using picoinjectors”, PNAS (2010), vol. 107, pp. 19163-19166. However, a significant challenge with picoinjection is that it is difficult to increase the size of the droplet to more than twice its initial volume. In another example—droplet merger—requires the formation of droplets much larger than the initial droplets to be synchronized with the injection of the initial droplets, which is a technically challenging procedure. While picoinjection solves the synchronization problem, it is not capable of increasing droplet volume to more than twice its initial volume. Accordingly, there is a need for an affordable and efficient system, method and kit for increasing the volume of a droplet by many times its initial volume to improve the performance and applicability of droplet-based microfluidics.
The following invention provides a system, method and kit for increasing the volume (and hence, size) of a droplet relative to the initial volume of the droplet, resulting in improved performance and applicability of droplet-based microfluidics.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.